The present invention relates to a tray for electronic components and more particularly to an electronic component tray used for conveying or inspecting electronic components known as semiconductor devices of a bowl grid array (BGA) type.
Electronic components of semiconductor devices known as semiconductor chips are composed of integrated circuits such as wafers. A typical example thereof includes an electronic component known as a BGA type semiconductor device. Such electronic components are known to be small-sized and required to be manufactured in a clean air environment.
Further, trays for electronic components are being used not only for conveying electronic components in the manufacturing process but also for efficiently handling electronic components for the purposes of inspection or prevention of electrostatic discharge damage thereof.
Conventionally used trays for electronic components include those as shown in FIG. 10, which trays are incorporated with electronic components and built up in a multi-layered laminated structure for use. It is to be noted that the electronic components are accommodated in cavities 51 defined between the vertically laminated trays.
Such trays are used for handling electronic components accommodated within the cavities 51 defined in a laminated manner. Said electronic components to be thus accommodated therein are constantly being downsized as explained with reference to FIG. 8, now to the level of a square having one side of 1 cm. The tray 50 for electronic components as shown in FIG. 10 is a case in point, in which a number of electronic components 100 are accommodated therein as so far explained. In said tray 50 for electronic components, square cavities 51 for accommodating components are regularly formed in a grid iron pattern.
Part of each cavity 51 is shown in an enlarged cross section in FIGS. 11 and 12, wherein the numeral 52 denotes a peripheral wall defining the cavity 51. In the drawings, said peripheral wall 52 has inside wall surfaces 52A inwardly sloping to make the cavity 51 in the form of a cone-shaped hollow to define a wide opening 53 at the top thereof.
Immediately below said peripheral wall 52, there is formed a peripheral wall 52B having a wall surface substantially vertical but having a slight inclination of for example 7 degrees to make a mold removing operation easy during an injection molding.
Further, a step 54 is formed immediately below said peripheral wall 52B, said step 54 extending inwardly of the cavity 51 in the form of a shelf to receive an electronic component 100 thereon.
Said step 54 has a peripheral wall surface 55 immediately therebelow substantially vertically but having a slight inclination of 7 degrees to make a mold removing operation easy. The space surrounded by said wall surface 55 is defined as an accommodation space 56 for contacts provided on one side of the board 100 for the electronic component 100. A flat floor 57 extends inwardly from the lowermost end of said peripheral wall surface 55. Said flat floor 57 is centrally formed with an opening 57A in the interest of weight saving and cost reduction of the tray.
Next, the explanation will go to the case in which electronic components 100 or BGA semiconductor chips are accommodated in the thus constructed tray 10 for electronic components. Said electronic components 100 are substantially square such that each component may be independently accommodated within the cavities 51 regularly arranged in the grid iron pattern. Each of said electronic components 100 has a plurality of semi-spherical contacts regularly arranged on the board 10, leaving a peripheral portion 103 with no contacts arranged thereat.
For example, if one side of the board 101 of the electronic component shown in FIG. 8 has a length of 4.45 mm, said peripheral portion 103 thereof has a width of 0.345 mm or less. Said board 101 is accommodated to allow said peripheral portion 103 to be placed on said step 54 such that the contacts will not come into abutment against any portion of said contact accommodation space 56.
It is noted in this connection that said board 101 has some allowance in its size. Therefore, if the electronic component 100 is caused to move sideways on the step 54, the contact provided on the farthest end position can come into abutment against the peripheral wall 55 and be damaged. Further in the worst case, if the tray built up in said laminated structure is turned over upside down, one side of the peripheral portion 103 of the board 101 can fall from the step 54 because said step 54 of the electronic board 100 has an apron as narrow as 0.5 mm with the result that a contact 102 descending to the lowest level contacts the floor 57 to be damaged.
With reference to FIG. 8 and FIG. 9, the electronic component tray 50 is formed of a planar member having components accommodation spaces 51 arranged in a grid iron pattern, each component accommodation space 51 having an area larger than the projected area of an electronic component 100 such that the electronic component is accommodated at the area including the step 54. The peripheral portion 103 thereof is sized sufficient to be received on the step 54. However, since the distance between the peripheral portions 103 or the length of the one side of the electronic component board 101 has an established tolerance to allow fluctuation in an actual product size to such an extent that the some component has a sufficient peripheral portion size to be received on the step 54 while others have insufficient sizes for this purpose.
In other words, with the peripheral portion 103 of an electronic component 100 being supported on the step 54, the gap defined between the circumference of the electronic component 100 and the inner surrounding wall 52B allows the electronic component to be received in an unneutral position with the result that the contact 102X can come into abutment against the inner surrounding wall 55 immediately below the step 54 and be damaged.
Further, if the peripheral portion 103A at one side of said electronic component 100 falls from said step 54, there is another risk that the semispherical contact 102X at the extremity of the floor in said contact accommodating space 56 can fracture upon abutment against the floor 57 of the contact accommodation space 56.
One of the causes for such trouble is considered to be the posture of the peripheral wall 55 formed substantially at a right angle with respect to the floor 57. For example, if the peripheral portion 103 at one side of the board 101 of the electronic components falls from the step 54, said board 101 falls directly down onto the floor 57 since there is no buffering support midway.